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Old 09-22-2020, 11:25 PM   #1
Kingpin1094
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Default DIY Dual In-tank Fuel Pumps

I wanted to see what people are going with these days for fuel setups. My sti currently makes 390whp on pump gas with a walboro 255. I have been thinking I want to start playing with some E85 and a flex fuel setup. I would like to be able to push my setup to 450whp on E, (might be turbo limited, but regardless I want the fuel setup ready to do that for the future).

I've been told I would want to either run a 340lph or 450lph, but to run those I believe id need a hardwire kit at minimum or a an upgraded FPC and both those are expensive.

I have found some older threads of people doing dual walboro 255's and having the second one switched with on at a certain boost pressure. (the first W255 is still run off the stock wiring connected to the FPC) This to me seems like the lowest cost easiest solution.

Parts list:
-2nd Walboro 255
-E85 and pressure rated tubing and clamps with a Y
-Inline 6 or 10 micron fuel filter (since factory needs to be removed)
-Some wire, a relay, and a pressure switch.

I'll probably also run an LED into the interior using another relay which will indicate when the second pump comes on. This will allow me to know when the second pump is on, and detect a potential failure early.

Any thoughts or insights into this plan? It seems good on paper to me but I wanted to get some other eyes on it and make sure its as simple as it seems.
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Old 09-23-2020, 04:11 AM   #2
00redobs
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Just run a "big" single fuel pump and be done with it. Hard-wire kits are cheap and relatively easy to install (Deatschwerks Fuel Pump Hardwire Kit).
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Old 09-23-2020, 08:28 AM   #3
Kingpin1094
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Quote:
Originally Posted by 00redobs View Post
Just run a "big" single fuel pump and be done with it. Hard-wire kits are cheap and relatively easy to install (Deatschwerks Fuel Pump Hardwire Kit).
The DW hardwire kit doesn't maintain the low medium high function does it?

Additionally at 450lph or larger I'd need a new FPC which iWire has as a $300 add on to their $250 hardwire kit.
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Old 09-23-2020, 09:29 AM   #4
BlackFighter
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There are a lot of threads already with this info, just need to search. At the same time I pushed 450whp with one pump. Don't know why people are going with 2 with such low hp levels. If you are concerned about Gs on turns then just get a surge tank.


https://forums.nasioc.com/forums/sho...ual+fuel+pumps

"One possible issue is that since all the fuel returns to the passenger side, at low fuel levels the driver's side pump will run dry which will reduce its life. The driver's side tank already has a fuel pickup that goes to a 'passive' pump on the passenger side that depends on the returning fuel flow to transfer fuel to the passenger side. And depending on exactly how the pickups are situated, you might still run into surge on some corners even with two pumps. A surge tank is really effective because there is absolutely no way for the fuel to move away from the fuel pump pickup (unless you're upside down maybe).

There is a recent thread on Scoobynet where someone posted about having a second pump, however he only turns it on manually when he believes he needs it and it dumps fuel onto the fuel sock of the other pump as opposed to being T-ed into the fuel line to the front of the car."
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Old 09-23-2020, 10:01 AM   #5
Kingpin1094
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Quote:
Originally Posted by BlackFighter View Post
There are a lot of threads already with this info, just need to search. At the same time I pushed 450whp with one pump. Don't know why people are going with 2 with such low hp levels. If you are concerned about Gs on turns then just get a surge tank.


https://forums.nasioc.com/forums/sho...ual+fuel+pumps

"One possible issue is that since all the fuel returns to the passenger side, at low fuel levels the driver's side pump will run dry which will reduce its life. The driver's side tank already has a fuel pickup that goes to a 'passive' pump on the passenger side that depends on the returning fuel flow to transfer fuel to the passenger side. And depending on exactly how the pickups are situated, you might still run into surge on some corners even with two pumps. A surge tank is really effective because there is absolutely no way for the fuel to move away from the fuel pump pickup (unless you're upside down maybe).

There is a recent thread on Scoobynet where someone posted about having a second pump, however he only turns it on manually when he believes he needs it and it dumps fuel onto the fuel sock of the other pump as opposed to being T-ed into the fuel line to the front of the car."
You made 450whp on E85 with which single fuel pump?

I don't think I track my car enough to justify the cost of a surge tank. I just want to be able to fuel my car to 450whp with E85, and I am trying to find the least expensive and easiest way to do it.
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Old 09-23-2020, 01:05 PM   #6
00redobs
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Quote:
Originally Posted by Kingpin1094 View Post
The DW hardwire kit doesn't maintain the low medium high function does it?

Additionally at 450lph or larger I'd need a new FPC which iWire has as a $300 add on to their $250 hardwire kit.
Hard-wire kits only provide power to the pump. Leave the ground (upgrade to bigger gauge wire) from the pump to FPC intact so your FPC can control duty cycles.

I run a Walbro 535LPH pump with a cheap Summit Racing hard-wire kit and stock FPC.

Last edited by 00redobs; 09-23-2020 at 01:16 PM.
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Old 09-23-2020, 02:23 PM   #7
JarHarms
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I would add that you should discuss with your tuner to see how they will be tuning the fuel pump. I find most tuners do not bother calibrating pump Duty Cycle (DC) and just change to 100% DC. A few tuners will retain stepped DC and should specify how/with what pump hardwire kit you are to use. Doing so might keep you from buying parts you don't use and re-buying parts you need. I bet most people have no idea if they are really tuned with 100%, factory stepped DC, or a modified stepped DC. They might think they know...but don't.
I agree with BlackFighter in that going overboard is just overboard here.

Last edited by JarHarms; 09-23-2020 at 02:29 PM.
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Old 09-23-2020, 03:55 PM   #8
Kingpin1094
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Quote:
Originally Posted by 00redobs View Post
Hard-wire kits only provide power to the pump. Leave the ground (upgrade to bigger gauge wire) from the pump to FPC intact so your FPC can control duty cycles.

I run a Walbro 535LPH pump with a cheap Summit Racing hard-wire kit and stock FPC.
Using a basic hardwire kit with the FPC still retains the stepped function? I was under the impression you needed the IWire kit for that. How long have you been runing the 535 on the stock FPC. I know IWire recommends above 450 replacing it due to the likihood of it burning out.

Quote:
Originally Posted by JarHarms View Post
I would add that you should discuss with your tuner to see how they will be tuning the fuel pump. I find most tuners do not bother calibrating pump Duty Cycle (DC) and just change to 100% DC. A few tuners will retain stepped DC and should specify how/with what pump hardwire kit you are to use. Doing so might keep you from buying parts you don't use and re-buying parts you need. I bet most people have no idea if they are really tuned with 100%, factory stepped DC, or a modified stepped DC. They might think they know...but don't.
I agree with BlackFighter in that going overboard is just overboard here.
I tune my own car. and still retain the factory 33% step function to keep the pump quieter at idle.
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Old 09-23-2020, 04:46 PM   #9
00redobs
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Quote:
Originally Posted by Kingpin1094 View Post
Using a basic hardwire kit with the FPC still retains the stepped function? I was under the impression you needed the IWire kit for that. How long have you been runing the 535 on the stock FPC. I know IWire recommends above 450 replacing it due to the likihood of it burning out.
As long as you keep the ground from the fuel pump to the FPC intact you'll have the stepped function.

I've been running the Walbro 535 and stock FPC since Oct. 2019. My car is on CarBerry so fuel pump duty cycles are 49% below 14PSI and 100% above 15PSI.
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Old 09-23-2020, 10:28 PM   #10
Kingpin1094
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Quote:
Originally Posted by 00redobs View Post
As long as you keep the ground from the fuel pump to the FPC intact you'll have the stepped function.

I've been running the Walbro 535 and stock FPC since Oct. 2019. My car is on CarBerry so fuel pump duty cycles are 49% below 14PSI and 100% above 15PSI.
Interesting, so what is the justification for Iwire's $250 hardwire kit when DW sells one for $40?
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Old 09-24-2020, 02:48 AM   #11
00redobs
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Quote:
Originally Posted by Kingpin1094 View Post
Interesting, so what is the justification for Iwire's $250 hardwire kit when DW sells one for $40?
iWire kit is plug and play.

DW kit is universal, you'll have to do some soldering work and trim or add some wire. Like I said before, its pretty easy if you know what you're doing.
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Old 09-24-2020, 12:43 PM   #12
Kingpin1094
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Quote:
Originally Posted by 00redobs View Post
iWire kit is plug and play.

DW kit is universal, you'll have to do some soldering work and trim or add some wire. Like I said before, its pretty easy if you know what you're doing.
Yea that's really no big deal. Well in that case ill just get a W450 and the universal hardwire kit which would be the cheapest and simplest solution.

I started down this path because the upgraded FPC and Iwire kit was $550 and I wanted to find a way to get the fueling I need on a budget.
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Old 09-24-2020, 10:07 PM   #13
benflynn
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How do we feel with adding an inline pump? I have a spare inline w255 laying around, Dw200 in the tank. Seems easy enough to hardwire an inline pump.
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